The present disclosure relates to semiconductor memory devices, and more particularly, relates to a storage device that stores data in a RAID manner.
A flash memory device is being widely used as voice and image data storage medium of an information device such as a computer, a smart phone, a digital camera, a camcorder, a voice recorder, a MP3 player, a handheld PC, and the like. However, a characteristic of flash memory is an erase operation is performed in advance to write data in a flash memory, and a unit of data being written is smaller than a unit of data being deleted. That characteristic becomes a factor that hinders use of a file system for a general hard disk as it is even in the case when a flash memory is used as an auxiliary memory device. In addition, that characteristic implies that a sequential input/output process of a memory is more efficient than a non-sequential input/output process.
A typical example of a flash memory-based high capacity storage device includes a SSD (solid state drive). As the demand for SSD increases, the uses of SSD are getting more variously divided. For example, the use of SSD may be subdivided into a SSD for server, a SSD for client, and a SSD for stripe set center. An interface of SSD should be able to provide an optimum speed and optimum reliability according to each use. A SATA, a PCIe, a SAS, etc. are applied as the optimum SSD interface to satisfy this requirement.
A storage system including a plurality of storage devices is used to secure high reliability. For example, a RAID (redundant array of independent disk) storage system divides data corresponding to one stripe set and distributively stores the divided stripes in the plurality of storage devices. Since it is unlikely that the plurality of storage devices causes a problem at the same time, this storage system can provide high reliability of data.